Differences in response to sensory input have long been observed in individuals with autism spectrum disorder (ASD) and are now included among the clinical diagnostic criteria for ASD. Although hyper- responsiveness to sensory stimuli has been emphasized in autobiographical accounts of ASD, empirical research suggests hypo-responsiveness better distinguishes ASD from both typical development and other developmental disabilities, and is more strongly associated with other ASD symptoms. The overarching goal of this proposal is to better understand atypical sensory processing as it relates to the social, behavioral, and communicative symptoms that characterize ASD. Because of the relatively slow development of visual acuity, sound and touch mediate a large proportion of early social interactions and experiences. These socially relevant auditory-tactile interactions rooted in infancy continue throughout development. For this reason, it is important to consider how audio-tactile processing might be affected in ASD and how changes in auditory and tactile function may relate to autism symptoms. The study of multisensory processing in the typical brain has established that combining signals from more than one sense can enhance the speed and accuracy of behavioral responses. Further, this enhancement is greatest when the individual signals being combined are weak or ambiguous. This latter concept, known as inverse effectiveness, could prove influential for the study and treatment of atypical sensory responsiveness in autism. This project aims to describe the perceptual and neural basis of auditory, tactile and audio-tactile (multisensory) responses in children with ASD and typically developing children using rigorous psychophysical methods and functional magnetic resonance imaging. We hypothesize that hypo-responsiveness to sound and touch will be associated with enhanced audio-tactile effects in ASD. If supported, these findings could have profound implications for the design of future interventions using sensory training. Furthermore, identifying brain regions which may contribute to altered sensory responsiveness could serve as biomarkers for early detection and as potential targets for the successful remediation of sensory related issues.